Does anyone make custom sized plastic holding tanks? I can't find anything that is quite the right size around 125 gallons.

The way I installed the drain valve on my current holding tank water the last 1/2" or so of water never drains and the tank stinks even after 6 months being empty. If I am going to replace the tank I would like to get a slightly larger one and one with a proper drain. There is a stainless fabricator locally that will make me one out of stainless for around $750 which I don't think is terrible since the plastic tanks I have seen are around $500 to $600 by the time they are shipped. Of course $500 to $600 is still less than $750 if I can find a custom plastic tank fabricator.

When I was buying my four tanks at Ronco I asked them about custom sizes - they said they could do them, but it would be a lot more expensive than a stock size for which they already have molds made. The guy stressed A LOT more expensive! They have nothing stock that will work for you? Even from their range of marine tanks (which have thicker walls)?

I had only looked at Ronco's RV tanks which only go up to 100 gallons max. I just looked at their marine tanks and they do make larger sizes, but it looks like they would cost me just as much as the custom stainless tank.

I'll call Custom Roto-Molding and see what they have to say about making a custom tank. Even though the name says custom I didn't see anything on their website about making a custom tank.

I wanted a 210gal single water tank-that Ronco made. But the box manufacturer made a slight mistake in the basement clearance and it wouldn't fit. I took back the tank and traded for two 98gal tanks that fit much better. If you're doing either your fresh or gray water tank, try tying two together to make better use of space. Good Luck, TomC

I'll check out Seelye too. I suspect from what I have read that the price for a custom plastic tank will be as much or more than a custom stainless tank. One big cost is shipping although Seelye might have no shipping. The stainless tank has no shipping costs and some of the large plastic tanks have to go freight.

I'm surprised nobody mentioned building a tank. I'm not confident that a welded plastic tank would stand up to 125 gallons of waste though.

I wanted a 210gal single water tank-that Ronco made. But the box manufacturer made a slight mistake in the basement clearance and it wouldn't fit. I took back the tank and traded for two 98gal tanks that fit much better. If you're doing either your fresh or gray water tank, try tying two together to make better use of space. Good Luck, TomC

I've already described my cramped under floor space in other threads (on the other Board). I had about 11" of depth and 23" wide but about 11' of length. So I did two tanks, each with a dump valve into a "Y" dump outlet. I have an electric lift pump to transfer grey into the black tank to maximize use - I'm expecting the grey to fill first. Then I can pull the cap off and run the waste hose to the dump site, drain the black and when it's empty, open the grey drain. The "backwash" will flush the black tank. This is how a two-waste-tank (grey and black) system works for me.

I had only looked at Ronco's RV tanks which only go up to 100 gallons max. I just looked at their marine tanks and they do make larger sizes, but it looks like they would cost me just as much as the custom stainless tank.

You shouldn't be paying Ronco's posted prices. Call them and ask for a price quotation - you may be pleasantly surprised . . .